1. Field of the Invention
The present invention relates to metal gratings and, more particularly, but not by way of limitation, to a method of manufacturing metal gratings that are easy of assembly yet very sturdy and reliable.
2. Description of the Prior Art
Metal gratings have been manufactured and used for a long number of years for providing a solid surface having open sectors for water drainage or air flow. Such gratings have been manufactured variously by cutting, stamping, welding and various combinations of such procedures in order to provide a flat surface having a relatively high percentage of open space therethrough for the purpose of providing walk-over cover for such as floor drains, gutters, and the like. U.S. Pat. No. 3,864,887 provides a teaching of an elongated grating which is constructed with spaced parallel rails fastened to transverse carrier bars. It utilizes an interlock construction wherein each elongated rail includes a lower zig-zag profile portion that slidably engages within a similar shaped zig-zag notching within the transverse carrier bar. A plurality of such longitudinal rails are secured within plural transverse carrier bars to constitute the elongated, rectangular grating.
U.S. Pat. No. 4,184,303 provides a similar teaching of a specially notched cross bar or tie bar which receives a plurality of T-shaped flooring rails slidably therein. This grating assembly is characterized by a relatively ornate cutting and forming procedure to provide the necessary slide mating and matching of members. U.S. Pat. No. 3,948,013 provides a steel grating formed of a plurality of spaced parallel bearing bars that are secured to one another in spaced relationship by plural parallel cross rods. The cross rods are cold forged into permanent engagement with the bearing bars to bring rigidity to the structure.
An early U.S. Pat. No. 1,335,623 provides a teaching wherein a plurality of elongated rails receive a plurality of square rods through mating holes. Each rail/rod juncture is provided with interlocking slotted engagement and the rail members are hammered or forged to retain the cross bars in final assembly. Finally, another early U.S. Pat. No. 1,620,846 provides a teaching wherein a plurality of cross bars are formed with a number of spaced upper slots, each of which receives a longitudinal bar therein. The longitudinal bars are then subjected to a punch press action at both an upper surface and a lower surface within the cross bar slot structure to cause a locking metal expansion thereby providing necessary rigidity to the elongated grating. Other U.S. Patents of more generalized nature relative to the present disclosure are submitted by Information Disclosure.